Jet Jet Tomography of Hot & Dense Matter Xin-Nian Wang LBNL, June 25, 2003.
Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National...
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Transcript of Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National...
![Page 1: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/1.jpg)
Third TECHQM Collaboration Meeting, CERN July 6-10, 2009
Xin-Nian WangLawrence Berkeley National Laboratory
The Brick Problem in High-Twist Approximation
in collaboration with Wei-tian Deng and Abhijit Majumder
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High-Twist Approach
e-
e-
Production & propagation in the same framework
However, a general proof of factorization is not done
Extension to Hevay-ion collisions:
Generalized Collinear Approx. in pQCD
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High-Twist approach to multiple scattering
Description of medium as collection of quasi-particle states
e-
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DGLAP Evolution in vacuum
Splitting function
q
p
k1 k2
p
q
perturbative region:
no matter how large is initial
![Page 5: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/5.jpg)
Induced gluon emission in twist expansion
q
Ap
xpxp
Ap
q
x1p+kT
transverse momentum of medium gluon
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Gauge Invariance
Expansion in kT
One should also consider
Final matrix elements should contain:
k
p
(not all models have this)
![Page 7: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/7.jpg)
Induced gluon emission in twist expansion
Collinear expansion:
Double scattering
Eikonal contribution to vacuum brems.
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Modified Fragmentation
Modified splitting functions
Guo & XNW’00
Two-parton correlation:
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Validity of collinear expansionCollinear expansion:
One has to re-sum higher-twist terms (Or model the behavior of small lT behavior)
Need to include all:
Region of validity: pQCD
If one is bold and goes beyond no one has gone before:
![Page 10: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/10.jpg)
Comparison with GLV
quasi-particle density
![Page 11: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/11.jpg)
11
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Modified DGLAP Evolution
Modified splitting functions
![Page 13: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/13.jpg)
Parton-gluon scattering
Quark-gluon Compton scattering
Schafer, XNW & Zhang 07
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The Brick Problem
Initial conditions:
![Page 15: Third TECHQM Collaboration Meeting, CERN July 6-10, 2009 Xin-Nian Wang Lawrence Berkeley National Laboratory The Brick Problem in High-Twist Approximation.](https://reader036.fdocuments.us/reader036/viewer/2022062523/5a4d1b157f8b9ab0599912db/html5/thumbnails/15.jpg)
Shower parton distr. in a gluon jet
g--> g
g --> q
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Shower parton distr. in a quark jet
q --> g
q--> qbar
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Valence quark energy loss
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Valence quark distribution
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Beyond the Brick Problem
Jet transport parameter
Jet transport parameter & phases of dense matter
Constrain “implementations” with DIS data (talk by Wei-tian Deng)
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Theoretical improvements
Elastic vs radiative: for finite E & L Qin, et al ‘’08
Recoil in radiative process:
Quark-annihilation Flavor changing process
q
Ap Ap
qNLO corrections to LO collinearfactorized contribution
Mass correction for heavy quarks
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Different cut-diagrams
+ …..